Backfire oil trap



Oct 22, 1940- F. A. DONALDSON BACKFIRE OIL TRAP Filed March 22, 1939 0 2I 0 o ow fmw b b 0 y p Patented Oct. 22, 1940 UNITED STATES I PATENTOFFICE Claims.

My present invention relates to improvements in air cleaners for use inconnection with the intakes of internal combustion engines and moreparticularly to that type of engine intake air cleaner embodying a bodyof fluid, usually oil.

More specifically stated, the invention relates to the novel manner offorming in air cleaners of this character means for trapping within thebody of the cleaner oil directed backwardly through the cleaner underinstantaneous back pressure surges resulting from engine backfire.

It is well recognized in the air cleaner art that in air cleaners of thetype referred to, and in which a body of fluid is employed as a dustcollecting medium, there is a tendency, under occasional backfireconditions of the engine through its intake, to blow oil from the oilreservoir of the cleaner outwardly through the intake conduit or passageof the air cleaner. Of course, if such backwardly directed oil ispermitted to be discharged from the cleaner through its intake not onlyis the eiliciency of the cleaner immediately impaired, but alsoconsiderable damage can be done by the discharged oil to machinery,buildings or the like on which the discharged oil may be deposited.

An. important object of the present invention is the provision of an oiltrapping arrangement incorporated entirely within the body of thecleaner. In accordance with the preferred arrangement hereinillustrated, the oil trapping arrangement is built into the body of thecleaner at only a very slight additional cost and with practically nosacrifice of capacity as compared 85 to similar cleaners of the sameexternal dimensions.

Another important object of the invention is the provision, in an aircleaner of the type incorporating a fiuid reservoir and an annular airinlet leading downwardly into the fluid reservoir, of a simple,inexpensive and highly eincient means for arresting, within the body ofthe cleaner, such oil as may be displaced from the oil well and directedbackwardly through the cleaner under instantaneous back pressure surges,resulting from engine backfire, during the brief duration of such backpressure surges.

The above and other highly important objects of the invention will bemade apparent from the following specification, claims and drawing.

In the accompanying drawing like characters indicate like parts.

Referring to the drawing:

55 The single figure thereof is a view in side elevation with some partsshown in section and some parts broken away, of an air cleanerincorporating a preferred embodiment of the invention.

The air cleaner illustrated includes a cylindrical casing shell I, whichshell is closed at its top 5 by a head 2 extending from which is an airoutlet conduit 3 that isadapted to be connected to the intake of aninternal combustion engine in the conventional manner. The bottom of thecylindrical casing shell 5 is normally closed by a cup- 1 like oilreservoir 4 that is normally filled with oil Y to the level indicated.lhis oil reservoir, 4 is preferably telescopically applied to the lowerend portion 5 of the cylindrical casing l and is normally removably heldin position tightly pressed against stop means preferably in the natureof an annular bead 6 of the cylindrical shell I through the medium ofclamping bolts l and anchoring brackets 8 and 9, the former of which areanchored to the casing shell l, and the latter of which are suitablyanchored to the oil reservoir 4.

For the purpose of providing an annular air inlet passage id' leadingdownwardly into the oil well from atmosphere there is provided withinthe shell I a depending inner skirt ll. This skirt ii is of smallerdiameter than the shell i except at its upper end portion where it isturned outwardly and anchored at l2 to the shell l thereby closing thetop of the annular air intake passage to the interior chamber of thecleaner.

The lower end portion of the skirt H, while concentrically disposed withrespect to the large upper portion thereof, is of reduced diameter, thelarge diameter upper section and smaller diameter lower section beingconnected by a radially or laterally extended annular portion Ila.Preferably and as illustrated, the smaller diameter lower section of theskirt it extends from a point somewhat above the normal static level ofthe oil 1 to a point below the normal static level of the oil well.

The upper end portion of the annular air intake passage ill communicateswith atmosphere through a plurality of perforations 63 on the shell 1. I

The lower end portion 5 of the shell I, which constitutes the outer wallof the annular intake passage Ill below the annular bead 6, is ofsubstantially the same diameter as the main shell section I above thehead 6 for a material extent axially, but is reduced materially indiameter at its lower end portion 96. The reduced diameter portion M isconnected to the large diameter upper portion of the shell section 5 bya laterally or radially extended port on I 5 that is axially spaced fromthe radial section Ila of the skirt II, so as to form with the saidportion I In an angular substantially radially disposed intake sectionI! intermediate the diflferent diameter upper and lower sections of theintake passa e ii.

As will be evident from the drawing, the oil reservoir 4 istclescopically applied over the larger diameter portion of the shellsection 5 and forms with the reduced diameter portion I4 and radialportion I5 of the shell section 5 an inverted annular channel I1overlying the fluid 1; immediately radially outwardly of the reduceddiameter end of the intake passage II. This inverted annular channel II,as will hereinafter be seen, serves as an oil trap under instantaneousbackfire conditions.

Mounted on the bottom of the oil reservoir 4 concentrically of the axisthereof, is an inner oil cup-forming annular flange I8 which ispreferably provided with. a plurality of oil metering openings I9. Thiscup-forming flange IO terminates with its upper edge preferably abovethe static fuel level in the reservoir and in approximately the sameplane as the radial skirtportion Ila.

The inner oil cup flange I8, being of smaller diameter than and beingconcentrically disposed with respect to the reduced diameter lowerportion of the skirt I I, forms with said skirt I I a reversely directedcontinuation IIIa of the annular air intake passage II that opens intoan expansion chamber 20 that is packed with a pervious filtering mediumpreferably in the nature of stacked corrugated wire screen elements II.The lower screen element II is seated on the ledge formed by the radialportion Ila of the skirt II.

Operation Under normal operating conditions in connection with aninternal combustion engine, for example, the interior of the cleanerwill be subjected to varying degrees of partial vacuum or subatmosphericpressure by virtue of the intake strokes of the engine pistons and theresultant predominant vacuum condition existing, under operatingconditions, in the intake manifold of the engine to which manifold itmay be assumed that the outlet conduit 3 is connected. As a result ofthis predominant sub-atmospheric pressure, air under atmosphericpressure will rush into the inlet passage II through the inletperforations I3 and will pass downwardly through the tortuous annularinlet passage I I and impinge against such oil as in the underlyingportion of the oil well.

This downwardly directed air will, of course, reverse its direction oftravel and pass upwardly into the expansion chamber 20 over the upperedge of the cup-forming flange through the upwardly directed portionIna, of the intake passage III. Under continuous operating conditions,most of the oil radially outward of the cup-forming flange I8 will bedisplaced and carried with the incoming air into the expansion chamberwhere it will be intercepted by the screen elements and permitted toflow downwardly toward the oil well.

This downward flow of oil will collect above the oil cup and build up ahead of oil over the oil cup it which will constantly tend to overflowthe edges of the cup and pass downwardly through the upwardly directedportion Illa of the intake passage, but the velocity of air movingthrough the intake passage will prevent such downward return of oilunder such operating conditions and will pick up such oil as tends tooverflow the cup and carry the same back into the upper interior portionof the expansion chamber only to be condensed on the screen elements andbe returned to the oil head above the oil cup I9.

Under conditions of backfire which cause the predominate sub-atmosphericcondition in the engine's intake to raise momentarily to a positive orplus atmospheric pressure, air will be directed downwardly through theexpansion chamber 20 and such downwardly directed air, when it strikesthe body of oil within the portion IIIa of the intake passage, will tendto blow all the oil radially outwardly of the cup flange Il upwardlyinto and through the intake passage I0, and, of course, if in theabsence of a suitable oil trap this is just what would happen. However,in the present structure a large part of this oil will be momentarilytrapped within the inverted annular channel I1, and such oil as is blowninto the lower end of the annular passage I0 above the lower end of theshell portion ll will, due to the abrupt outward turn in the intakepassage II between wall portions Na and I5, be deflected and thrownagainst the outer shell or casing I. The oil thus thrown against andspread over a wall of the passage will have its velocity sufficientlyretarded by surface friction to keep it from reaching the perforations I3 during the very brief period of the back-fire surge.

, From the above it will be evident that the offset in the lower endportion 5 of the shell I serves two important functions, to wit: (a) toprovide an oil trap reservoir, and (b) to provide one wall of a tortuouspassage .which causes such oil as may be blown into the intake to bedistributed over the wall surfaces thereof to thereby retard itsvelocity and prevent its reaching the flnal point of outlet during thebrief period of the back pressure surge. Tests of this cleaner underbackfire conditions both with and without the portions I4 and ll of theouter wall of the inlet passage conclusively prove the merits of thisdevice as an oil trap. For example, when this arrangement isincorporated, even under quite severe backfire conditions, little if anyoil is discharged from the perforations I3; whereas, in the absence ofthis arrangement last described under similar backfire conditions oil isdischarged from the perforations I3 at very high velocity. As previouslyindicated, such backflring of oil to atmosphere results in immediatelylowered efflciency of the cleaner due to the lowering of the fuel levelin the well reservoir, and is further serious in that the discharged oilis apt to result in serious damage or at least the dirting of any objectwith which it comes in contact. A still further serious result ofbackflring of oil through the inlet of the cleaner is that the oiling upof the surface of the primary intake passage or perforations results inthe rapid collection of dirt in these passages which rapidly increasesthe restriction of the device and thereby reduces the efficiency of theengine to which it is connected.

From a manufacturing point of view the fact that the lower section 5 ofthe shell I is primarily formed as a separate unit and the manner inwhich it is anchored or attached to the shell section I is veryimportant. In the flrst place, it is cheaper to form the lower section 5of the shell as a separate unit than it would be to form a similarcontour directly on the end of the main shell section I, and even afterthis was done. it would require an operation to form a suitable annularbead to act as a stop for the oil reservoir 4. According to the presentscheme, the lower end of the shell section I and the adjacent upper endportion of the lower section thereof are each provided with out-turnedflanges which are joined by rolling one of these flanges around theother thereof.

What I claim is:

1. In an air cleaner, a cylindrical shell made up of a main uppersection and a relatively short lower section, said upper and lower shellsections being provided at their point of jointure with outturnedannular flanges one of which is rolled over the other thereof to securethe two together, the said lower shell section immediately below saidflangesbeing of approximately the same diameter as the said uppersection but being of reduced diameter at its lower portion, a cup-likeoil receptacle telescopically applied over the larger diameter upperportion of the lower shell section to the limit permitted by the joinedannular flanges of the sections, an annular skirt flange concentricallydisposed within the interior oi the shell and being of less diameterthan said shell so as to provide therebetween and said shell an annularair intake passage, said skirt extending downwardly from theintermediate portion 0! the shell to the vicinity of the normal staticoil level therein, means closing of! communication between the top ofsaid annular air intake passage and the interior of the shell, and airinlet opening through thehpper shell section.

2. The structure deflned in claim 1 in which the said skirt which formsthe inner wall of the annular air intake passage is shaped toapproximately correspond to the contour of the reduced diameter portionof the lower shell section.

3. In an air cleaner, a cylindrical shell having a reduced diameterlower end portion and a radially outwardly projecting stop means locatednear the bottom oi the shell but above the reduced diameter portionthereof, a cup-like oil receptacle telescopically flt over the largestdiameter portion of the cylindrical shell below said stop means to thelimit permitted by engagement of the top 0! the oil receptacle with thesaid stop means, a cylindrical skirt concentrically disposed within theshell section and extending into the oil receptacle, said skirt beingspaced from the sides of the shell to form therewith an annular intakepassage terminating in the oil receptacle at a point below the reduceddiameter lower end of said shell, the reduced diameter lower end portionof the shell section being spaced from the adjacent wall portions of theoil receptacle to form therewith, and within the oil receptacle, adownwardly opening oil trapping channel radially outwardly of thedischarge end portion of the annular intake passage.

4. In an air cleaner, a cylindrical shell having a reduced diameterlower end portion, a cup-like oil receptacle telescopically engaging thelower end portion of the cylindrical shell above said reduced diameterportion, a cylindrical skirt concentrically disposed within the shellsection and extending into the oil receptacle, said skirt being spacedfrom the sides of the shell to form therewith an annular air intakepassage terminating in the oil receptacle at a point below the reduceddiameter lower end 01 said shell, the reduced diameter lower end portionof the shell section being spaced from the adjacent wall portions of theoil receptacle to form therewith, and within the oil receptacle, adownwardly opening oil trapping channel radially outwardly oi thedischarge end portion oi the annular air intake passage.

5, The structure deflned in claim 4 in which the said skirt, which formsthe inner wall of the annular air intake passage, is shaped toapproximately correspond to the contour of the reduced diameter lowerend portion of said shell.

FRANK A. DONALDSON.

